Some Critical Issues for Injection Molding

This book is composed of different chapters which are related to the subject of injection molding and written by leading international academic experts in the field. It contains introduction on polymer PVT measurements and two main application areas of polymer PVT data in injection molding, optimization for injection molding process, Powder Injection Molding which comprises Ceramic Injection Molding and Metal Injection Molding, ans some special techniques or applications in injection molding. It provides some clear presentation of injection molding process and equipment to direct people in plastics manufacturing to solve problems and avoid costly errors. With useful, fundamental information for knowing and optimizing the injection molding operation, the readers could gain some working knowledge of the injection molding

Review on the Brownian Dynamics Simulation of Bead-Rod-Spring Models Encountered in Computational Rheology

Kinetic theory is a mathematical framework intended to relate directly the most relevant characteristics of the molecular structure to the rheological behavior of the bulk system. In other words, kinetic theory is a micro-to-macro approach for solving the flow of complex fluids that circumvents the use of closure relations and offers a better physical description of the phenomena involved in the flow processes. Cornerstone models in kinetic theory employ beads, rods and springs for mimicking the molecular structure of the complex fluid. The generalized bead-rod-spring chain includes the most basic models in kinetic theory: the freely jointed bead-spring chain and the freely-jointed bead-rod chain. Configuration of simple coarse-grained models can be represented by an equivalent Fokker-Planck (FP) diffusion equation, which describes the evolution of the configuration distribution function in the physical and configurational spaces. FP equation can be a complex mathematical object, given its multidimensionality, and solving it explicitly can become a difficult task. Even more, in some cases, obtaining an equivalent FP equation is not possible given the complexity of the coarse-grained molecular model. Brownian dynamics can be employed as an alternative extensive numerical method for approaching the configuration distribution function of a given kinetic-theory model that avoid obtaining and/or resolving explicitly an equivalent FP equation. The validity of this discrete approach is based on the mathematical equivalence between a continuous diffusion equation and a stochastic differential equation as demonstrated by Itô in the 1940s. This paper presents a review of the fundamental issues in the BD simulation of the linear viscoelastic behavior of bead-rod-spring coarse grained models in dilute solution. In the first part of this work, the BD numerical technique is introduced. An overview of the mathematical framework of the BD and a review of the scope of applications are presented. Subsequently, the links between the rheology of complex fluids, the kinetic theory and the BD technique are established at the light of the stochastic nature of the bead-rod-spring models. Finally, the pertinence of the present state-of-the-art review is explained in terms of the increasing interest for the stochastic micro-to-macro approaches for solving complex fluids problems. In the second part of this paper, a detailed description of the BD algorithm used for simulating a small-amplitude oscillatory deformation test is given. Dynamic properties are employed throughout this work to characterise the linear viscoelastic behavior of bead-rod-spring models in dilute solution. In the third and fourth part of this article, an extensive discussion about the main issues of a BD simulation in linear viscoelasticity of diluted suspensions is tackled at the light of the classical multi-bead-spring chain model and the multi-bead-rod chain model, respectively. Kinematic formulations, integration schemes and expressions to calculate the stress tensor are revised for several classical models: Rouse and Zimm theories in the case of multi-bead-spring chains, and Kramers chain and semi-flexible filaments in the case of multi-bead-rod chains. The implemented BD technique is, on the one hand, validated in front of the analytical or exact numerical solutions known of the equivalent FP equations for those classic kinetic theory models; and, on the other hand, is control-set thanks to the analysis of the main numerical issues involved in a BD simulation. Finally, the review paper is closed by some concluding remarks

Novel polyurethane/graphene nanocomposite coatings

A series of graphene based conductive and anticorrosion coatings were developed in this project. Multi layer coating consists of EPD pristine graphene coating, PU/graphene primer and PU/graphene topcoat was developed. A simple mechanical chemical approach was suggested to fabricate graphene with low cost and high efficiency. XRD was used to characterize the exfoliation efficiency of graphite. TEM was used to examine the size of the graphene sheets. SEM was used to characterize the surface morphology of the coatings. The particle size of all the carbon materials used was characterised by Malvern particle sizer. FTIR and XPS were used to characterize the chemical composition of the graphene powder and the coatings fabricated. MDSC and FTIR were used to monitor the cure dynamic of PU. [Continues.]</div

Polysulfide Mitigation at the Electrode-Electrolyte Interface: Experiments in Rechargeable Lithium Sulfur Batteries

In the field of energy storage technology, the lithium sulfur battery is intensely studied in interest of its great theoretical gravimetric capacity (1672 Ah kg–1) and gravimetric density (2600 Wh kg–1). The theoretical performance values satisfy viability thresholds for petroleum–free electric vehicles and other emerging technologies. However, this elusive technology remains in the research sector due to a wealth of challenges resulting from its complex chalcogenide electrochemistry. The most infamous challenge remains the polysulfide redox shuttle, a phenomenon in which lithium polysulfide intermediates are produced as elemental sulfur S8 is reduced to lithium sulfide Li2S during the discharge cycle. Because the higher order polysulfides are soluble in organic electrolyte, battery cycling can result in dissolution of the cathode, dendrite formation upon the lithium metal anode, and passivation of electrode surfaces. These problems can ultimately cause rapid capacity fade and unstable Coulombic efficiency. As lithium sulfur battery research enters its 3rd decade, it is becoming increasingly clear that solutions will be holistic or synergistic; that is, addressing the aforementioned issues by suppressing their source in the polysulfide redox shuttle rather than isolated symptoms of the underlying mechanism. This thesis serves as a summary of research performed to study polysulfide suppression and mitigation through electrode material synthesis, electrolyte design, and in situ characterization. Synthesis techniques include solid state pyrolysis, autogenic synthesis, and ultrasound sonochemistry. Material characterization techniques include isothermal nitrogen sorption; scanning, transmission, and scanning transmission electron microscopy; thermogravimetric analysis; energy dispersive X–ray spectroscopy; organic elemental analysis; X– ray diffraction; and Raman spectroscopy. Electrochemical characterization includes galvanostatic battery cycling, differential potentiometric analysis, and electrochemical impedance spectroscopy. Altogether, this research demonstrates the challenges of polysulfide degradation are not sufficiently addressed by symptomatic approaches. Synthesis pathways for carbon sulfur cathodes that encourage homogeneous sulfur distribution (i.e., autogenic or sonochemical synthesis) improve specific capacity across extended cycling, but show excessive polysulfide production at slow cycling rates. In combination with fluorinated electrolyte, carbon sulfur cathode morphology improves Coulombic efficiency at cycling rates between C/20 — 2 C but at the cost of gravimetric capacity. Synchrotron tomography characterization, developed for Advanced Photon Source Beamline 6–BM–A, evidences that fluorinated electrolytes may also effectively suppress dendrite formation on lithium metal anodes. This suggests more holistic and optimized techniques, or their combinations, may lead to effective polysulfide suppression and successful commercialization of the lithium sulfur battery. Supplementary research explores broader impact of synthesized carbon applications in lithium sulfur batteries. Pyrolysis synthesis processes are evaluated for health and environment impacts using optical by–product sizing and life cycle analysis, respectively. In the context of pyrolytic synthesis of carbon microsheets, micro and nano-sized carbonaceous particulate by–products released during synthesis must be collected to minimize health exposure risks. The environmental impact of this synthesis process is a function of mode of oxygen deficiency, that is, whether pyrolytic atmosphere is facilitated by vacuum or inert gas stream. Finally, submicron carbon spheres, a carbon morphology produced by pyrolysis of sonochemically-synthesized polymer spheres, demonstrate gravimetric capacity which is a strong function of microstructure (i.e., pore distribution, crystallite size, structural disorder). In turn, microstructural properties are determined by synthesis temperature, a dimension of synthesis pathway

Development of Solution Blow Spun Nanofibers as Electrical and Whole Cell Biosensing Interfaces

Infectious pathogens place a huge burden on the US economy with more than $120 billion spent annually for direct and indirect costs for the treatment of infectious diseases. Rapid detection schemes continue to evolve in order to meet the demand of early diagnosis. In chronic wound infections, bacterial load is capable of impeding the healing process. Additionally, bacterial virulence production works coherently with bacterial load to produce toxins and molecules that prolongs the healing cycle. This work examines the use of nonwoven polymeric conductive and non-conductive nanofiber mats as synthetic biosensor scaffolds, drug delivery and biosensor interface constructs. A custom-made nanofiber platform was built to produce solution blow spun nanofibers of various polymer loading. Antimicrobial nanofiber mats were made with the use of an in-situ silver chemical reduction method. Ceria nanoparticles were incorporated to provide an additional antioxidative property. Conductivity properties were examined by using silver and multi-walled carbon nanotubes (MWCNT) as a filler material. SBS parameters were adjusted to analyze electrical conductivity properties. Nanofiber mats were used to detect bacteria concentrations in vitro. Protein adhesion to conductive nanofibers was studied using fluorescent antibodies and BCA assay. Anti-rabbit and streptavidin Alexa Flour 594 was used to examine the adsorption properties of SBS nanofiber mats. Enhancements were made to further improve interface design for specificity. SBS nanofiber electrodes were fabricated to serve as scaffold and detection site for spike protein detection. Bacteria virulence production was examined by the detection of pyocyanin and quorum sensing molecules. The opportunistic pathogen, Pseudomonas aeruginosa is a nosocomial iii pathogen found in immunocompromised patients with such as those with chronic wounds and cystic fibrosis. Pyocyanin is one of four quorum sensing molecules that the pathogen produces which can be detected electrochemically due to its inherent redox-active activity. SBS has been used to develop a sensing scheme to detect pyocyanin. This work also examines the use of a synthetic biosensor with a LasR based system capable of detecting homoserine lactone produced by P. aeruginosa and other common gram-negative pathogens. Genetic modifications were made to biosensor in order to replace a green, fluorescent reporter with a chromoprotein based reporter system for visual readout. Additionally, work related to community service and outreach regarding the encouragement of middle school students to pursue Science, Technology, Engineering and Math (STEM) was conducted. Results from outreach program showed an increase in the STEM interest among a group of middle school students. There was a general trend with STEM career knowledge, STEM self-efficacy and the level of interest in STEM careers and activities. Military research was also done with the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) to develop several assays for the detection of several highly infectious viruses and bacteria. Due to confidentiality, the work cannot be published in this manuscript

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids

Solving the Matter - Crystal Engineering and Particle Design of Poorly Soluble Drugs via Rapid Expansion of Supercritical Solutions

A growing number of new drug candidates are highly lipophilic. Statistically, 40 % of new drug molecules are thus excluded from further development at the early stages of pharmaceutical research. From a technological standpoint, particle design and crystal engineering are valuable tools to increase intrinsic solubility and low dissolution rates of lipophilic compounds. However, traditional pharmaceutical processing techniques make ample use of organic solvents and rough process conditions. This causes stability issues of the drug products and contradicts today's growing demand for sustainable technologies. In contrast, the Rapid Expansion of Supercritical Solutions (RESS) can provide both mild process conditions and a solvent-free processing technology. With the development of three RESS applications for micronization, nanotechnology and crystal engineering, the dissolution rate of poorly soluble compounds could be improved distinctly in this thesis. RESS thus offers a valuable technology platform with an up-to-date unexploited potential to enhance the future sector of pharmaceutical formulation science